Erectopus: a French theropod pieced together from a lost collection

Erectopus superbus is a predatory theropod from the Early Cretaceous of northeastern France. Its story is unusual: some original bones disappeared, its scientific name changed more than once, and its modern diagnosis had to be rebuilt from surviving elements, casts and old descriptions. Erectopus is both a diagnosable fossil taxon and a case study in the limits of research when a historic collection is lost.

Quick facts

Phosphatic sands near Louppy-le-Château

The remains were found in the early 1870s near Louppy-le-Château in the Meuse department. They came from the phosphatic sands of La Penthiève, in the mammillatum ammonite zone of the Lower Albian. The locality is about 113–110 million years old. Those beds formed in a coastal marine setting and also preserve marine reptiles and crocodylomorphs. A land theropod’s bones may have been carried toward the coast before burial. Marine sediment identifies where the bones were buried, not a permanently aquatic habitat or a marine hunting lifestyle.

Henri-Émile Sauvage mentioned teeth in 1876 and described more material in 1882 as Megalosaurus superbus. In the nineteenth century, “Megalosaurus” was often used as a catch-all for large predatory dinosaur remains that had not yet been sorted into natural groups. The name was a starting interpretation, not evidence that the French animal was closely related to the English Megalosaurus.

How the name Erectopus emerged

Friedrich von Huene recognised in 1923 that the French bones differed from Megalosaurus and erected the genus Erectopus. A later combination, Erectopus sauvagei, appeared in the literature, so material from the same historic collection circulated under different species names. In 2005 Ronan Allain reviewed the available specimens and naming history. He concluded that the teeth and skeletal elements described by Sauvage belonged to one taxon and that the name with priority was Erectopus superbus. The material is now associated with the museum number MNHN 2001-4.

By the time of the modern revision, Louis Pierson’s private collection had been dispersed. Some bones were missing, but casts survived, as did an incomplete upper-jaw bone with teeth. A cast preserves the outside shape of an absent object; it cannot be inspected for internal structure, surface details or restoration in the same way as the original. The distinction matters when a diagnosis depends on small anatomical features.

Which bones define the animal?

The material attributed to Erectopus includes part of a maxilla, teeth, hand bones, a femur, sections of the tibia, a calcaneum and the second metatarsal. These bones do not form an articulated skeleton. Their association relies on the collection history, shared provenance and anatomical compatibility. Researchers therefore work with a composite sample whose elements do not all have the same evidential status.

Allain identified a combination of features in the upper jaw, femur, ankle and foot. These include the rounded anterior process of the maxilla, the shape of the femoral head and shaft, features of the calcaneum and the proportions of the second metatarsal. One previously reported “unique” bend in the femur proved to be an effect of preparation and restoration rather than real anatomy. That episode is more than a technical footnote: adhesive, plaster and damage must not be mistaken for evolutionary characters.

An allosauroid, with appropriate caution

The lower leg and the interpreted shape of the ankle led Allain to place Erectopus within Allosauroidea. Later reviews have treated it as a non-carcharodontosaurid allosauroid, possibly near metriacanthosaurids. This places it on a broad theropod branch that also includes Allosaurus, but it does not make the French animal a close copy of that better-known genus.

Fragmentary anatomy leaves room for alternatives. Analyses based mainly on teeth have sometimes grouped the material with abelisaurids, but similar tooth shapes can evolve independently in different predators. A cautious summary is that Erectopus was a basal tetanuran and probably an allosauroid. Comparing it with Acrocanthosaurus or Concavenator helps explain its proposed position, but does not establish that it had their body proportions, a sail or other distinctive features.

Estimating size from a thigh bone

An older account gave the femur a length of about 48 centimetres. A modern measurement of the MNHN 2001-4 cast is approximately 45.2 centimetres; the second metatarsal is about 23 centimetres. Comparisons with more complete theropods suggest a total length around four to five metres. That is a medium-sized predator, not a giant. The range depends on which relative proportions are used, because the skull, vertebral column and most limbs are unknown. A mass of roughly 200–300 kilograms has been proposed, but it was not measured directly from a complete body.

The laterally compressed teeth curve backwards and carry cutting edges, supporting a carnivorous diet. They could grip and slice soft tissue. The available fossils do not identify specific prey, hunting tactics or scavenging behaviour: no stomach contents, coprolites or securely matched bite marks accompany the remains.

What a reconstruction can show

The broad outline is that of a bipedal theropod with powerful hind limbs and a toothed head. A length of four to five metres communicates scale, but details beyond the preserved part of the upper jaw must be borrowed from relatives. No crests, skin covering, complete tail or front limbs are known for this genus. Those missing parts may be restored for an illustration, but they remain comparisons rather than discoveries.

The isolated collection does not reveal whether Erectopus lived in groups, how fast it moved or where it nested. A coastal scene in an illustration is a reconstruction of the depositional landscape, not a recorded moment from the animal’s life. Explore it alongside other predators in the dinosaur catalogue. Its importance lies in the rarity of diagnostic Albian theropods in Europe and in the revealing history of a museum revision.